Produção e caracterização microestrutural de ligas Ti-Zr-Si-B

Abstract

Materials consisting of intermetallic compounds have been evaluated for structural applications in high temperature and in this context, the Ti-Si-B system alloys present potential for these applications, due to their phases, in particular the ternary phase Ti6Si2B. The present work aimed to produce Ti- xZr-20Si-10B (x = 5, 7, 10, 15 and 20%-at) system alloys by high energy milling and subsequent spark plasma sintering and evaluate the effect of zirconium addition on phase transformations and stability of Ti6Si2B compound. During the milling, samples were taken during 20, 60, 180, 300, 420 and 600 minutes. Mixtures of powdered and sintered alloys powders were characterized by scanning electron microscopy, x-ray diffraction, optical microscopy and energy dispersive spectroscopy. Morphologies of the powders were evaluated and the phase transformations involved in the process of high ball milling and sintering. It was noted that for higher zirconium contents, fracture mechanisms were highlighted and Ti5Si3 was formed for all compositions. Subsequently Spark Plasma Sintering, it could be observed the formation of phases TiSS, Ti5Si3, Ti6Si2B for 5 to 10 (%.) of zirconium, while for higher contents, 15 and 20 (%.) of zirconium predominant phases in microstructures were Ti3Si and Ti5Si3, TiB. The increasing of zirconium content, it was noted the decrease in ternary compound, Ti6Si2B, whereas for Ti15Zr20Si10B and Ti20Zr20Si10B alloys, were not detected significant signs of this compound and, in addition, it promoted the higher solubility of silicon in other phases.